Control of drag reduction by the spanwise Lorentz force in turbulent channel flow
When objects move in a viscous fluid, the turbulent boundary-layer could lead to an increase of friction drag.Many control approaches have been studied to modify the structures of the boundary layer.In this paper, the control of turbulent channel flow by space-dependent Lorentz force and the mechanism of drag reduction are investigated with direct numerical simulation (DNS) methods for different Reynolds numbers.With the application of optimal Lorentz force, the in-depth relations among characteristic structures in the flow field, mean Reynolds shear stress and the effect of drag reduction for different Reynolds numbers are discussed.The results indicate that the maximum drag reductions can be obtained with an optimal combination of parameters for each case of different Reynolds numbers.The regular quasi-streamwise vortex structures, which appear in the flow field,have the same period with that of Lorentz force.These structures suppress the random velocity fluctuations, which lead to the absolute value of mean Reynolds shear stress decreasing and moving away from the wall.Moreover, the wave number of optimal Lorentz force increases and the scale of the regular quasi-streamwise vortex structures decreases as the Reynolds number raises up.Therefore, the rate of drag reduction decreases with the increase of Reynolds number since the scale of the regular quasi-streamwise vortex structures decreases.
Flow control Drag reduction Lorentz force Turbulent channel flow
Dai-wen JIANG Yang HAN Hui ZHANG Zi-jie ZHAO
Science and Technology on Transient Physics Laboratory, Nanjing University of Science and Technology, Nanjing 210094, China
国际会议
2018 International Conference on Defence Technology (2018国际防务技术会议)
北京
英文
898-903
2018-10-21（万方平台首次上网日期，不代表论文的发表时间）